Electronic components are used in ever increasing numbers of consumer and commercial electronic products. Examples of some of these consumer and commercial products are televisions, personal computers, Internet servers, cell phones, pagers, palm-type organizers, portable radios, car stereos, or remote controls. As the demand for these consumer and commercial electronics increases, there is also a demand for those same products to become smaller, more functional, more cost efficient and thermally efficient, and more portable for consumers and businesses.
As a result of the size decrease in these products, the components that comprise the products must also become smaller, better manufactured and better designed. Examples of some of those components that need to be reduced in size or scaled down are printed circuit or wiring boards, resistors, wiring, keyboards, touch pads, and chip packaging.
Components, therefore, are being broken down and investigated to determine if there are better building materials and methods that will allow them to be scaled down and/or combined to accommodate the demands for smaller electronic components. In layered components, one goal appears to be decreasing the number of the layers while at the same time increasing the functionality and durability of the remaining layers, decreasing the production steps and increasing the cost efficiency. These tasks can be difficult, however, given that the number of layers cannot readily be reduced without sacrificing functionality.
Also, as electronic devices become smaller and operate at higher speeds, energy emitted in the form of heat increases dramatically. A popular practice in the industry is to use thermal grease, or grease-like materials, alone or on a carrier in such devices to transfer the excess heat dissipated across physical interfaces. The most common types of thermal interface materials are thermal greases, phase change materials, and elastomer tapes. Thermal greases or phase change materials have lower thermal resistance than elastomer tape because of the ability to be spread in very thin layers and provide intimate contact between adjacent surfaces. Typical thermal impedance values range between 0.1-1.6° C. cm2/W. However, a serious drawback of thermal grease is that thermal performance deteriorates significantly after thermal cycling, such as from 65° C. to 150° C., or after power cycling when used in VLSI chips. It has also been found that the performance of these materials deteriorates when large deviations from surface planarity causes gaps to form between the mating surfaces in the electronic devices, or when large gaps between mating surfaces are present for other reasons, such as manufacturing tolerances, etc. When the heat transferability of these materials breaks down, the performance of the electronic device in which they are used is adversely affected.
Organic pastes and epoxies are also being used to facilitate heat removal from the component. One example of this use is applying the organic paste and/or epoxy to the interface between the silicon and a heat spreader, such as a nickel plated copper spreader. These pastes and epoxies are normally filled with metal or other thermally conductive particles to improve heat transfer. As components are becoming smaller and more complex, the amount of heat to be removed has increased to the point where solid metal thermal interface is necessary. In most conventional applications, the solid metal thermal interface is a solder material of melting point 140-200° C.
As more solder materials are being utilized in components to dissipate heat, it has been discovered that it is difficult to solder to nickel without the use of a material, such as a flux, because of the production of detrimental nickel oxides at the solder-nickel interface. One recent approach to completing the solder joint without the use of a flux is to electrodeposit a gold spot on the precise location where the solder joint is to be formed. This approach is described in U.S. Pat. No. 6,504,242 issued to Deppisch et al. (Jan. 7, 2003). While this approach works well functionally, the value of gold contained within the spot is detrimental to the cost efficiency of the components. Furthermore, in order to complete a joint having a gold spot or gold interface, there are at least two process steps necessary—deposition of the gold and application of the solder material. These additional process steps are not only costly, but slow.
Thus, there is a continuing need to: a) design and produce thermal interconnects and thermal interface materials, layered materials, components and products that meet customer specifications while minimizing the size of the device and number of layers; b) produce more efficient and better designed materials, products and/or components with respect to the compatibility requirements of the material, component or finished product; c) develop reliable methods of producing desired thermal interconnect materials, thermal interface materials and layered materials and components/products comprising contemplated thermal interface and layered materials; d) develop materials that possess a high thermal conductivity and a high mechanical compliance; and e) effectively reduce the number of production steps necessary for a package assembly, which in turn results in a lower cost of ownership over other conventional layered materials and processes.